In hearing devices, such as hearing aids, background noise is detrimental to the intelligibility of speech sounds. Most modern hearing devices address this issue by introducing noise reduction processing technology into the microphone output signal paths. The aim is to increase the Signal-to-Noise (SNR) ratio available to listeners, hence improve clarity and ease of listening to the hearing device wearer.
The success of noise reduction processing often depends greatly on the formation of appropriate reference signals to estimate the noise, the reason being that the reference signal is used to optimize an adaptive filter that aims to eliminate the noise, ideally leaving only the target signal. However, such reference estimates are often inaccurate because most known techniques, such as Voice Activity Detection, are susceptible to errors. In turn, such inaccuracies lead to inappropriate filtering and degradation in the output quality of processed sound (target distortion), particularly at low SNR where noise reduction functions are most needed.